Merge branch 'linus' into x86/pat2

Conflicts:
	arch/x86/mm/init_64.c

1 files changed, 232 insertions, 58 deletions

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 8f98e9de1b8..161bb850fc4 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -104,7 +104,7 @@ __setup("notsc", notsc_setup);
 /*
  * Read TSC and the reference counters. Take care of SMI disturbance
  */
-static u64 tsc_read_refs(u64 *pm, u64 *hpet)
+static u64 tsc_read_refs(u64 *p, int hpet)
 {
 	u64 t1, t2;
 	int i;
@@ -112,9 +112,9 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet)
 	for (i = 0; i < MAX_RETRIES; i++) {
 		t1 = get_cycles();
 		if (hpet)
-			*hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
+			*p = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
 		else
-			*pm = acpi_pm_read_early();
+			*p = acpi_pm_read_early();
 		t2 = get_cycles();
 		if ((t2 - t1) < SMI_TRESHOLD)
 			return t2;
@@ -123,13 +123,59 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet)
 }
 
 /*
+ * Calculate the TSC frequency from HPET reference
+ */
+static unsigned long calc_hpet_ref(u64 deltatsc, u64 hpet1, u64 hpet2)
+{
+	u64 tmp;
+
+	if (hpet2 < hpet1)
+		hpet2 += 0x100000000ULL;
+	hpet2 -= hpet1;
+	tmp = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
+	do_div(tmp, 1000000);
+	do_div(deltatsc, tmp);
+
+	return (unsigned long) deltatsc;
+}
+
+/*
+ * Calculate the TSC frequency from PMTimer reference
+ */
+static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2)
+{
+	u64 tmp;
+
+	if (!pm1 && !pm2)
+		return ULONG_MAX;
+
+	if (pm2 < pm1)
+		pm2 += (u64)ACPI_PM_OVRRUN;
+	pm2 -= pm1;
+	tmp = pm2 * 1000000000LL;
+	do_div(tmp, PMTMR_TICKS_PER_SEC);
+	do_div(deltatsc, tmp);
+
+	return (unsigned long) deltatsc;
+}
+
+#define CAL_MS		10
+#define CAL_LATCH	(CLOCK_TICK_RATE / (1000 / CAL_MS))
+#define CAL_PIT_LOOPS	1000
+
+#define CAL2_MS		50
+#define CAL2_LATCH	(CLOCK_TICK_RATE / (1000 / CAL2_MS))
+#define CAL2_PIT_LOOPS	5000
+
+
+/*
  * Try to calibrate the TSC against the Programmable
  * Interrupt Timer and return the frequency of the TSC
  * in kHz.
  *
  * Return ULONG_MAX on failure to calibrate.
  */
-static unsigned long pit_calibrate_tsc(void)
+static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin)
 {
 	u64 tsc, t1, t2, delta;
 	unsigned long tscmin, tscmax;
@@ -144,8 +190,8 @@ static unsigned long pit_calibrate_tsc(void)
 	 * (LSB then MSB) to begin countdown.
 	 */
 	outb(0xb0, 0x43);
-	outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
-	outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
+	outb(latch & 0xff, 0x42);
+	outb(latch >> 8, 0x42);
 
 	tsc = t1 = t2 = get_cycles();
 
@@ -166,31 +212,154 @@ static unsigned long pit_calibrate_tsc(void)
 	/*
 	 * Sanity checks:
 	 *
-	 * If we were not able to read the PIT more than 5000
+	 * If we were not able to read the PIT more than loopmin
 	 * times, then we have been hit by a massive SMI
 	 *
 	 * If the maximum is 10 times larger than the minimum,
 	 * then we got hit by an SMI as well.
 	 */
-	if (pitcnt < 5000 || tscmax > 10 * tscmin)
+	if (pitcnt < loopmin || tscmax > 10 * tscmin)
 		return ULONG_MAX;
 
 	/* Calculate the PIT value */
 	delta = t2 - t1;
-	do_div(delta, 50);
+	do_div(delta, ms);
 	return delta;
 }
 
+/*
+ * This reads the current MSB of the PIT counter, and
+ * checks if we are running on sufficiently fast and
+ * non-virtualized hardware.
+ *
+ * Our expectations are:
+ *
+ *  - the PIT is running at roughly 1.19MHz
+ *
+ *  - each IO is going to take about 1us on real hardware,
+ *    but we allow it to be much faster (by a factor of 10) or
+ *    _slightly_ slower (ie we allow up to a 2us read+counter
+ *    update - anything else implies a unacceptably slow CPU
+ *    or PIT for the fast calibration to work.
+ *
+ *  - with 256 PIT ticks to read the value, we have 214us to
+ *    see the same MSB (and overhead like doing a single TSC
+ *    read per MSB value etc).
+ *
+ *  - We're doing 2 reads per loop (LSB, MSB), and we expect
+ *    them each to take about a microsecond on real hardware.
+ *    So we expect a count value of around 100. But we'll be
+ *    generous, and accept anything over 50.
+ *
+ *  - if the PIT is stuck, and we see *many* more reads, we
+ *    return early (and the next caller of pit_expect_msb()
+ *    then consider it a failure when they don't see the
+ *    next expected value).
+ *
+ * These expectations mean that we know that we have seen the
+ * transition from one expected value to another with a fairly
+ * high accuracy, and we didn't miss any events. We can thus
+ * use the TSC value at the transitions to calculate a pretty
+ * good value for the TSC frequencty.
+ */
+static inline int pit_expect_msb(unsigned char val)
+{
+	int count = 0;
+
+	for (count = 0; count < 50000; count++) {
+		/* Ignore LSB */
+		inb(0x42);
+		if (inb(0x42) != val)
+			break;
+	}
+	return count > 50;
+}
+
+/*
+ * How many MSB values do we want to see? We aim for a
+ * 15ms calibration, which assuming a 2us counter read
+ * error should give us roughly 150 ppm precision for
+ * the calibration.
+ */
+#define QUICK_PIT_MS 15
+#define QUICK_PIT_ITERATIONS (QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256)
+
+static unsigned long quick_pit_calibrate(void)
+{
+	/* Set the Gate high, disable speaker */
+	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
+
+	/*
+	 * Counter 2, mode 0 (one-shot), binary count
+	 *
+	 * NOTE! Mode 2 decrements by two (and then the
+	 * output is flipped each time, giving the same
+	 * final output frequency as a decrement-by-one),
+	 * so mode 0 is much better when looking at the
+	 * individual counts.
+	 */
+	outb(0xb0, 0x43);
+
+	/* Start at 0xffff */
+	outb(0xff, 0x42);
+	outb(0xff, 0x42);
+
+	if (pit_expect_msb(0xff)) {
+		int i;
+		u64 t1, t2, delta;
+		unsigned char expect = 0xfe;
+
+		t1 = get_cycles();
+		for (i = 0; i < QUICK_PIT_ITERATIONS; i++, expect--) {
+			if (!pit_expect_msb(expect))
+				goto failed;
+		}
+		t2 = get_cycles();
+
+		/*
+		 * Make sure we can rely on the second TSC timestamp:
+		 */
+		if (!pit_expect_msb(expect))
+			goto failed;
+
+		/*
+		 * Ok, if we get here, then we've seen the
+		 * MSB of the PIT decrement QUICK_PIT_ITERATIONS
+		 * times, and each MSB had many hits, so we never
+		 * had any sudden jumps.
+		 *
+		 * As a result, we can depend on there not being
+		 * any odd delays anywhere, and the TSC reads are
+		 * reliable.
+		 *
+		 * kHz = ticks / time-in-seconds / 1000;
+		 * kHz = (t2 - t1) / (QPI * 256 / PIT_TICK_RATE) / 1000
+		 * kHz = ((t2 - t1) * PIT_TICK_RATE) / (QPI * 256 * 1000)
+		 */
+		delta = (t2 - t1)*PIT_TICK_RATE;
+		do_div(delta, QUICK_PIT_ITERATIONS*256*1000);
+		printk("Fast TSC calibration using PIT\n");
+		return delta;
+	}
+failed:
+	return 0;
+}
 
 /**
  * native_calibrate_tsc - calibrate the tsc on boot
  */
 unsigned long native_calibrate_tsc(void)
 {
-	u64 tsc1, tsc2, delta, pm1, pm2, hpet1, hpet2;
+	u64 tsc1, tsc2, delta, ref1, ref2;
 	unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
-	unsigned long flags;
-	int hpet = is_hpet_enabled(), i;
+	unsigned long flags, latch, ms, fast_calibrate;
+	int hpet = is_hpet_enabled(), i, loopmin;
+
+	local_irq_save(flags);
+	fast_calibrate = quick_pit_calibrate();
+	local_irq_restore(flags);
+	if (fast_calibrate)
+		return fast_calibrate;
 
 	/*
 	 * Run 5 calibration loops to get the lowest frequency value
@@ -216,7 +385,13 @@ unsigned long native_calibrate_tsc(void)
 	 * calibration delay loop as we have to wait for a certain
 	 * amount of time anyway.
 	 */
-	for (i = 0; i < 5; i++) {
+
+	/* Preset PIT loop values */
+	latch = CAL_LATCH;
+	ms = CAL_MS;
+	loopmin = CAL_PIT_LOOPS;
+
+	for (i = 0; i < 3; i++) {
 		unsigned long tsc_pit_khz;
 
 		/*
@@ -226,16 +401,16 @@ unsigned long native_calibrate_tsc(void)
 		 * read the end value.
 		 */
 		local_irq_save(flags);
-		tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL);
-		tsc_pit_khz = pit_calibrate_tsc();
-		tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
+		tsc1 = tsc_read_refs(&ref1, hpet);
+		tsc_pit_khz = pit_calibrate_tsc(latch, ms, loopmin);
+		tsc2 = tsc_read_refs(&ref2, hpet);
 		local_irq_restore(flags);
 
 		/* Pick the lowest PIT TSC calibration so far */
 		tsc_pit_min = min(tsc_pit_min, tsc_pit_khz);
 
 		/* hpet or pmtimer available ? */
-		if (!hpet && !pm1 && !pm2)
+		if (!hpet && !ref1 && !ref2)
 			continue;
 
 		/* Check, whether the sampling was disturbed by an SMI */
@@ -243,23 +418,41 @@ unsigned long native_calibrate_tsc(void)
 			continue;
 
 		tsc2 = (tsc2 - tsc1) * 1000000LL;
+		if (hpet)
+			tsc2 = calc_hpet_ref(tsc2, ref1, ref2);
+		else
+			tsc2 = calc_pmtimer_ref(tsc2, ref1, ref2);
 
-		if (hpet) {
-			if (hpet2 < hpet1)
-				hpet2 += 0x100000000ULL;
-			hpet2 -= hpet1;
-			tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
-			do_div(tsc1, 1000000);
-		} else {
-			if (pm2 < pm1)
-				pm2 += (u64)ACPI_PM_OVRRUN;
-			pm2 -= pm1;
-			tsc1 = pm2 * 1000000000LL;
-			do_div(tsc1, PMTMR_TICKS_PER_SEC);
+		tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2);
+
+		/* Check the reference deviation */
+		delta = ((u64) tsc_pit_min) * 100;
+		do_div(delta, tsc_ref_min);
+
+		/*
+		 * If both calibration results are inside a 10% window
+		 * then we can be sure, that the calibration
+		 * succeeded. We break out of the loop right away. We
+		 * use the reference value, as it is more precise.
+		 */
+		if (delta >= 90 && delta <= 110) {
+			printk(KERN_INFO
+			       "TSC: PIT calibration matches %s. %d loops\n",
+			       hpet ? "HPET" : "PMTIMER", i + 1);
+			return tsc_ref_min;
 		}
 
-		do_div(tsc2, tsc1);
-		tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2);
+		/*
+		 * Check whether PIT failed more than once. This
+		 * happens in virtualized environments. We need to
+		 * give the virtual PC a slightly longer timeframe for
+		 * the HPET/PMTIMER to make the result precise.
+		 */
+		if (i == 1 && tsc_pit_min == ULONG_MAX) {
+			latch = CAL2_LATCH;
+			ms = CAL2_MS;
+			loopmin = CAL2_PIT_LOOPS;
+		}
 	}
 
 	/*
@@ -270,7 +463,7 @@ unsigned long native_calibrate_tsc(void)
 		printk(KERN_WARNING "TSC: Unable to calibrate against PIT\n");
 
 		/* We don't have an alternative source, disable TSC */
-		if (!hpet && !pm1 && !pm2) {
+		if (!hpet && !ref1 && !ref2) {
 			printk("TSC: No reference (HPET/PMTIMER) available\n");
 			return 0;
 		}
@@ -278,7 +471,7 @@ unsigned long native_calibrate_tsc(void)
 		/* The alternative source failed as well, disable TSC */
 		if (tsc_ref_min == ULONG_MAX) {
 			printk(KERN_WARNING "TSC: HPET/PMTIMER calibration "
-			       "failed due to SMI disturbance.\n");
+			       "failed.\n");
 			return 0;
 		}
 
@@ -290,44 +483,25 @@ unsigned long native_calibrate_tsc(void)
 	}
 
 	/* We don't have an alternative source, use the PIT calibration value */
-	if (!hpet && !pm1 && !pm2) {
+	if (!hpet && !ref1 && !ref2) {
 		printk(KERN_INFO "TSC: Using PIT calibration value\n");
 		return tsc_pit_min;
 	}
 
 	/* The alternative source failed, use the PIT calibration value */
 	if (tsc_ref_min == ULONG_MAX) {
-		printk(KERN_WARNING "TSC: HPET/PMTIMER calibration failed due "
-		       "to SMI disturbance. Using PIT calibration\n");
+		printk(KERN_WARNING "TSC: HPET/PMTIMER calibration failed. "
+		       "Using PIT calibration\n");
 		return tsc_pit_min;
 	}
 
-	/* Check the reference deviation */
-	delta = ((u64) tsc_pit_min) * 100;
-	do_div(delta, tsc_ref_min);
-
-	/*
-	 * If both calibration results are inside a 5% window, the we
-	 * use the lower frequency of those as it is probably the
-	 * closest estimate.
-	 */
-	if (delta >= 95 && delta <= 105) {
-		printk(KERN_INFO "TSC: PIT calibration confirmed by %s.\n",
-		       hpet ? "HPET" : "PMTIMER");
-		printk(KERN_INFO "TSC: using %s calibration value\n",
-		       tsc_pit_min <= tsc_ref_min ? "PIT" :
-		       hpet ? "HPET" : "PMTIMER");
-		return tsc_pit_min <= tsc_ref_min ? tsc_pit_min : tsc_ref_min;
-	}
-
-	printk(KERN_WARNING "TSC: PIT calibration deviates from %s: %lu %lu.\n",
-	       hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min);
-
 	/*
 	 * The calibration values differ too much. In doubt, we use
 	 * the PIT value as we know that there are PMTIMERs around
-	 * running at double speed.
+	 * running at double speed. At least we let the user know:
 	 */
+	printk(KERN_WARNING "TSC: PIT calibration deviates from %s: %lu %lu.\n",
+	       hpet ? "HPET" : "PMTIMER", tsc_pit_min, tsc_ref_min);
 	printk(KERN_INFO "TSC: Using PIT calibration value\n");
 	return tsc_pit_min;
 }